15. the ratio pv to nrt is plotted against pressure for ch4 at 0°c and 200°c. why does the curve for 0°c drop below the horizontal line for an ideal gas whereas the curve for 200°c does not?
a) at 200°c, the molecules can overcome intermolecular attractions.
b) at 200°c, the volume of individual molecules becomes negligible.
c) at 200°c, the forces between molecules become repulsive.

A) At 200 °C, the molecules can overcome intermolecular attractions.

Explanation:

At 200 °C, the molecules can overcome intermolecular attractions, so the exerted pressure by the movement of the molecules  increases and the positive deviation from ideal gas behavior occurs.

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